全文获取类型
收费全文 | 6577篇 |
免费 | 877篇 |
国内免费 | 410篇 |
专业分类
电工技术 | 1346篇 |
综合类 | 676篇 |
化学工业 | 635篇 |
金属工艺 | 200篇 |
机械仪表 | 400篇 |
建筑科学 | 271篇 |
矿业工程 | 163篇 |
能源动力 | 204篇 |
轻工业 | 214篇 |
水利工程 | 90篇 |
石油天然气 | 263篇 |
武器工业 | 72篇 |
无线电 | 1419篇 |
一般工业技术 | 595篇 |
冶金工业 | 231篇 |
原子能技术 | 87篇 |
自动化技术 | 998篇 |
出版年
2024年 | 25篇 |
2023年 | 59篇 |
2022年 | 126篇 |
2021年 | 187篇 |
2020年 | 195篇 |
2019年 | 188篇 |
2018年 | 155篇 |
2017年 | 260篇 |
2016年 | 250篇 |
2015年 | 306篇 |
2014年 | 408篇 |
2013年 | 397篇 |
2012年 | 506篇 |
2011年 | 507篇 |
2010年 | 410篇 |
2009年 | 418篇 |
2008年 | 411篇 |
2007年 | 476篇 |
2006年 | 371篇 |
2005年 | 339篇 |
2004年 | 262篇 |
2003年 | 275篇 |
2002年 | 232篇 |
2001年 | 190篇 |
2000年 | 174篇 |
1999年 | 116篇 |
1998年 | 108篇 |
1997年 | 80篇 |
1996年 | 70篇 |
1995年 | 60篇 |
1994年 | 56篇 |
1993年 | 36篇 |
1992年 | 40篇 |
1991年 | 32篇 |
1990年 | 31篇 |
1989年 | 26篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1974年 | 3篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1964年 | 3篇 |
1962年 | 2篇 |
1961年 | 2篇 |
排序方式: 共有7864条查询结果,搜索用时 31 毫秒
31.
The calculations of gas solubilities in supercritical solvents require equations of state remaining accurate in the critical range, which are difficult to obtain with classical models. In this work, the Helmholtz energy of a mixture is considered as the sum of the Helmholtz energies of pure components taken at a constant packing fraction and of a residual term which may have the form of a RedlichKister, Van Laar, NRTL, UNIQUAC, or UNIFAC function. Thus it is possible to assign to a given component an equation of state whose form is different from that of the others. This model has been applied to binary systems containing supercritical carbon dioxide. The results are improved with respect to those obtained with the classical model for vapor-liquid equilibria and for volumetric properties. 相似文献
32.
一步法合成松香改性酚醛树脂 总被引:2,自引:0,他引:2
探讨了一步法合成松香改性酚醛树脂的反应机理,确定了最佳原料组成及合成工艺,由此制备出高溶解粘度和矿油容纳度的松香改性酚醛树脂,是一种性能优异的高级胶印油墨连接料 相似文献
33.
Hiroaki Yamada Toshihiko Tanaka Shigeyuki Funabiki 《Electrical Engineering in Japan》2006,157(4):56-65
This paper proposes a novel method of suppressing the inrush current of transformers. A small‐rated voltage‐source PWM converter is connected in series to the transformers through a matching transformer. As the connected PWM converter serves as a resistor for the source current, no inrush phenomena occurs. The required rating of the PWM converter, which serves as the damping resistor for the inrush phenomena, is 1/400 that of the main transformers in single‐phase circuits. In three‐phase circuits, it is 1/900. The basic principle of the proposed method is discussed. Digital computer simulation is implemented to confirm the validity and excellent practicability of the proposed method using the PSCAD/EMTDC. A prototype experimental model is constructed and tested. The experimental results demonstrate that the proposed method can perfectly suppress the inrush phenomena. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(4): 56–65, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20174 相似文献
34.
线性联合检测算法在TD-SCDMA系统中的性能分析与比较 总被引:18,自引:3,他引:15
时分、同步码分多址(TD-SCDMA)系统是基于时分双工(TDD)的块传输系统,它使用了联合检测这项关键技术来抵抗符号间干扰(ISI)和多址干扰(MAI)。以上行链路为例,本文分析了三种线性联合检测算法--匹配滤波块均衡器(MF-BLE)、迫零块均衡器(ZF-BLE)和最小均方误差块均衡器(MMSE-BLE)。从理论上,我们描述了这三种线性联合检测算法的基本原理,并对它们进行了比较(包括抗干扰性能和计算量)。随后,我们模拟了不同参数条件下(信道模型、码道数目、天线数目)这几种算法的性能,并与理论分析进行对照,得出一定结论。 相似文献
35.
高压供电设备故障特别是输电线路的高压接地故障对工地的影响是相当大的。由于接地故障为隐性故障,没有明显的物理现象,且若是长期接地可能会发展成较为严重的两相或三相短路故障,使系统解列运行直至崩溃;由于工地流动人员较多,还易造成电击事故。利用高压一相接地时在线路中产生零序电压这一特性来迅速判断和切除接地的用电设备,可以保证各项施工的顺利进行。 相似文献
36.
Qin Datong Sun DongyeState Key Laboratory ofMechanical Transmission Chongqing University Chongqing China 《机械工程学报(英文版)》2003,16(4):391-395
The rmomechnical phenomena occurring between friction pairs greatly change the distributions oflining pressure and friction surface temperature of a multiple disc wet brake. It has become one of the maincauses of brake failure. In order to understand these thermomechanical phenomena, several design and mate-rial factors tha have great influence on thermomechanical phenomena, such as heat transfer coefficient, fric-tion factor, sliding velocity initial lining pressure and so on, are analyzed. An isothermal design method isproposed for designing a multiple disc wet brake. 相似文献
37.
38.
L. Rutigliano D. Fino G. Saracco V. Specchia P. Spinelli 《Journal of Applied Electrochemistry》2008,38(7):1035-1041
This paper describes the results obtained from an electrokinetic treatment of a real soil polluted by lead acetate. Powdered
soil samples were pressed with a consolidometer till 100 kPa to obtain cylindrical specimens with the same characteristics
as a subsoil. Tests were carried out in a Perspex electrochemical cell where soil specimens were introduced with a hollow
punch. A low intensity direct current was applied in order to remove contaminants, due to electrophoresis and electroosmosis
phenomena. The water flow, conductivity, apparent electroosmotic coefficient, as well as other characteristic parameters,
were measured throughout the test. The water content and degree of pore saturation were estimated at the beginning and end
of the test. The soil slab was divided into four slices and the Pb concentration profile determined. The main factor governing
the extraction of contaminant was found to be the pH in the acidic range. Indeed, under these conditions high removal efficiencies
could be reached. These results could lead to the design of a new electrochemical treatment cell equipped with a cationic
membrane to expand the region of favourable pH within the soil. 相似文献
39.
The dielectric behavior of sol-gel derived Ba0.80Sr0.20(ZrxTi1−x)O3 (0.0 ≤ x ≤ 0.50) thin films is studied. A relaxor behavior is observed for x ≥ 0.35. The degree of relaxation increases with Zr content. The frequency dependence of the polar regions follows Vogel-Fulcher relation with a characteristic cooperative freezing at freezing temperature (Tf). Below Tf, a long range polarization ordering is likely to take place. The plausible mechanism of the relaxor behavior of BSZT thin films with Zr contents ≥ 0.35 has been proposed based on the measured temperature as well as frequency dependent dielectric data. The solid solution system is visualized as a mixture of Ti+ 4 rich polar regions and Zr+ 4 rich regions; with the increase in Zr content the volume fraction of the polar regions is progressively reduced. At and above 35.0 at.% Zr substitution the polar regions exhibit typical relaxor behavior. 相似文献
40.